Rechargeable batteries and capacitors are widely used in many industries, and generally include a group of two or more secondary cells (or secondary batteries, or capacitors). Generally, rechargeable batteries, such as Lithium, Nickel, lead-acid, flow type batteries or the like, and supercapacitors such as double-layer capacitors or the like, require a main switching circuit for charging and/or discharging operations between the respective energy-storage device and a charging/discharging circuit including a power source and/or load. To compensate for switching ripple currents during electric power conversion in the charging/discharging equipment, the charging/discharging circuit may include or be otherwise coupled to large-capacity condensers (capacitors), which may be charged before charging an energy-storage pack including one or more energy-storage devices in order to control ripple current.
Recently high-rate batteries and supercapacitors have been recently developed, and introduced for electric vehicle (EV) and hybrid-electric vehicle (HEV) applications. These high-rate energy-storage devices generally require larger electrical energy during charging or discharging operations, and have a much higher electro-energy density with much lower internal impedance as compared to other batteries and supercapacitors. This higher electro-density with lower internal impedance, however, may undesirably result in an excessively-large initial current when the main switching circuit is engaged under some unpredictable situation between the condensers and high-rate energy-storage devices. And this excessively large initial current may result in sparking and/or burning of switching relay terminals, and may thereby lead to a reduction in the useful life of those relay terminals.